It might seem counter-intuitive to think that attacking the Islamic State, also known as ISIS or ISIL, would damage Iran or Shi’ite interests in the Middle East. After all, Iran shares the West’s concerns about the radical Sunni group and is in a tacit alliance with the United States when it comes to defeating their common enemy. And yet, Iran fears it might end up being the loser in this battle.
The 2003 U.S.-led war in Iraq opened a new political vista in favor of Iran — and Shi’ism — by replacing Sunni leaders, like Saddam Hussein, with Shi’ite politicians previously in exile in Iran, like Nouri al-Maliki.
This shift in the balance of power between Shi’ites and Sunnis led to the emergence of a crescent-shaped region in the Middle East with a majority Shi’ite population under Tehran’s sphere of influence.
Since Islamic State first emerged, The Islamic Republic of Iran believed the group was engineered by Arab states of the Gulf, particularly Saudi Arabia and Qatar. On these grounds, it took it upon itself to fight against the extremist militants. When Islamic State occupied the province of Mosul, Iran wholeheartedly cooperated with the Iraqi Kurds as well as the Iraqi forces to contain further advancement of the Islamic State.
There is mounting evidence that Saudi Arabia and Qatar, in turn, provided financial and military support to the opponents of the Assad regime. To achieve this aim, they did not hesitate to engage the most fundamentalist of Islamist groups, such as Al Qaeda’s affiliates Al Nusra and Islamic State.